This invention relates to hydrostatic supporting apparatus which supports, without physical contact, a mobile part which moves relatively to a load-bearing part.
Hydrostatic supporting devices in various forms are already known. One type is the so-called fixed bearing arrangement, wherein hydraulic fluid is supplied in a throttled manner and at a constant rate to a bearing pocket, or several such pockets, in a non-displaceable portion of the load-bearing part. The pressure in the pocket or pockets is influenced to such a great extent by the spacing between the mobile and load-bearing parts that the force vs. travel diagram for these devices resembles a vertical line. Therefore, if the mobile part moves slightly away from the loadbearing part, the device will cease to provide any substantial support.
Another type of known hydrostatic supporting device is the so-called follow-up arrangement. This kind of apparatus differs from the first type in that hydraulic fluid is supplied to the pocket or pockets at a constant pressure, rather than a constant rate. As a result, the force vs. travel diagram for these devices is a horizontal line, i.e., they afford a constant supporting force regardless of displacement of the mobile part.
In a third type of hydrostatic supporting device proposed in the prior art, the bearing pocket or pockets are formed in a displaceable piston which is urged toward the mobile part by the pressure in the chamber of an associated hydraulic supporting motor. Each bearing pocket is connected with the motor chamber via a throttled passage, and the supporting piston is provided with an elastic element which also urges it in the direction of the mobile part. The force vs. travel characteristic of this type of device is an inclined straight line, i.e., the supporting force increases and decreases, respectively, as the mobile part moves toward and away from the load-bearing part. However, the elastic element sometimes is heavy and can be adjusted only by applying considerable force.